1. Field of the Invention
This invention relates to a stack device, more particularly to a stack device capable of removing dust particles, sulfur oxides and nitrogen oxides from a stack gas.
2. Description of the Related Art
In the prior art, a conventional stack device includes an apparatus for removing dust and sulfur oxides of a stack gas, and a stack gas passage through which the stack gas passes. The apparatus has a plurality of first spraying units with first nozzles which spray an aqueous alkaline solution toward the central axis of the stack device in order to produce an alkaline mist. The first spraying units are mounted at the intermediate section of the passage of the stack device. A mist extractor is provided in the passage near the top of the stack device. A second spraying unit is mounted below the mist extractor. The second spraying unit has a plurality of second spray nozzles which spray the aqueous alkaline solution downward in order to produce an alkaline mist below the mist extractor. Dust and sulfur oxides contained in the stack gas adhere to the condensed drops of the alkaline mist and are removed from the stack gas. Waste, consisting essentially of alkaline solution, dust and sulfur oxides, is collected in a settling tank. However, it is noted that the alkaline mist in the stack device cannot remove nitrogen oxides contained in the stack gas. In addition, water in the waste collected in the settling tank is not reused.